Environment variables specific to Blender? Do they exist?
Environment Variables:
  $BLENDER_USER_CONFIG      Directory for user configuration files.
  $BLENDER_USER_SCRIPTS     Directory for user scripts.
  $BLENDER_SYSTEM_SCRIPTS   Directory for system wide scripts.
  $BLENDER_USER_DATAFILES   Directory for user data files (icons, translations, ..).
  $BLENDER_SYSTEM_DATAFILES Directory for system wide data files.
  $BLENDER_SYSTEM_PYTHON    Directory for system python libraries.
  $TMP or $TMPDIR           Store temporary files here.
  $SDL_AUDIODRIVER          LibSDL audio driver - alsa, esd, dma.
  $PYTHONHOME               Path to the python directory, eg. /usr/lib/python.


But the best way is to modify your prefs (File->path) as said above.